1. Field of the Invention
The present invention relates to a printing apparatus for forming a print image on a printing medium and a printing method.
2. Description of the Related Art
An inkjet printer as one type of printing apparatus forms a print image on a printing medium by discharging ink.
An inkjet printer has a print head for discharging ink, a carriage including the print head, a drive unit for reciprocating the carriage in the main scanning direction, and a conveyance unit for conveying a printing medium in the sub-scanning direction almost perpendicular to the main scanning direction. Note that the print head has a plurality of nozzles each including a plurality of ink discharge orifices.
In a printing apparatus with the above arrangement, due to deflection of a carriage shaft which serves as a guide when the carriage reciprocates or the like, a print image shifts in a direction parallel to the sub-scanning direction with respect to an image based on image data.
FIG. 25 is a view showing a case in which an image is printed on a printing medium (for example, a printing paper sheet) using image data by discharging ink from a print head. It is ideal to print an image 901 shown in FIG. 25. If, however, a carriage shaft is deflected, ink droplet adhering positions on a printing medium actually shifts in the sub-scanning direction, and an image 902 shown in FIG. 25 is thus printed.
To avoid this, there is provided a method of limiting nozzles to be used among a plurality of nozzles, and a method of printing while shifting a printing position for each color in accordance with a shift amount of the printing position. Furthermore, Japanese Patent Laid-Open No. 2009-040043 discloses a method of switching between the two above-described methods depending on the condition involved.
In the above-described method of limiting nozzles to be used, a time taken to form a print image becomes long.
Even if the method of shifting a printing position for each color in accordance with a shift amount of the printing position is used, it is impossible to sufficiently correct the shift of the print image, thereby not allowing to obtain a high quality print image.